The time of origin of orchids is in dispute, although Dressler suggests that they originated 80 to 40 million years ago (Mya; late Cretaceous to late Eocene) [ 6].
But scientists had been unable to pin down the time of origin or find supporting fossil evidence.
Potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock.
In Bartlett's Quotations, 16th edition, Justin Kaplan threw up his hands and listed it only as a saying, with no attribution or guess at time of origin.
Ionium-thorium dating, method of establishing the time of origin of marine sediments according to the amount of ionium and thorium they contain.
Even younger than open clusters, stellar associations are very loose groupings of young stars that share a common place and time of origin but that are not generally tied closely enough together gravitationally to form a stable cluster.
This yielded a tracer with a well-defined time of origin that will be useful long into the future for following the course of such water in soils and aquifers (water-bearing layers of rock).
However, the time of origin is unknown during a real-time tsunami forecast.
Until recently, that was all that could be said about the time of origin based on fossils.
Was it developed independently by different populations or spread throughout Africa from a single point and time of origin?
